This invention relates to a frame saw and a method of simultaneously sawing a relatively thick piece of wood, referred to as the xe2x80x9cfeed stockxe2x80x9d, into a plurality of thinner pieces suitable for use as veneer, lattice, window louvers or slats, and as the plies of engineered three-ply flooring.
In general, frame saws accomplish this by mounting a plurality of saw blades within a frame. The blades are parallel to each other and spaced apart by the desired thickness of the sawn thinner pieces. The thickness of the blades themselves represents wastage, so the blades are made to be as thin as possible and are held within the frame under tension sufficient to maintain the blades in a straight, taut condition at all times. The blades are reciprocated rapidly up and down. These blades have teeth which are angled to cut on the downstroke, the feed stock being supported on a feed table. No cutting takes place on the upstroke. Thus, in prior art frame saws the movement of the feed stock must be stopped during the upward, non-cutting stroke, otherwise the face of cuts would bear against and damage or break the blades. This requires a mechanism timed to the reciprocation of the blades to continuously start and stop the movement of the feed stock in timed relation with the reciprocation of the blades. When the blades are moving downwardly in the cutting stroke the stock is being fed. When the blades are being reciprocated upwardly into the position to begin the next downward cutting stroke, the stock is stationary.
This arrangement requires a complicated mechanism which reduces the efficiency of the machine and the quality of the processed stock. If the feed stock is still moving during any part of the upstroke the back side of the saw teeth can damage the feed stock, and can be damaged by contact with the feed stock at the face of the last cut.
The present invention provides an efficient, electronic means of permitting the stock to be continuously fed through the frame saw apparatus, thus eliminating the costly and inefficient necessity to constantly start and stop the movement of the stock during each reciprocation. In general, this is accomplished by moving the saw frame carriage carrying the saw blades downstream during the non-cutting upstroke and moving the saw blades upstream during the cutting downstroke. The upstream movement of the blades and the downstream movement of the stock permits a deeper cut during each reciprocation of the saw frame carriage.
Therefore, it is an object of the invention to provide a frame saw apparatus which allows continuous travel of the feed stock through the frame saw apparatus.
It is another object of the invention to provide a frame saw apparatus which permits an increased depth of cut during each cutting stroke.
It is another object of the invention to provide a frame saw apparatus produces a feed stock product more efficiently and at a higher quality.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a frame saw for sawing a relatively thick piece of wooden feed stock simultaneously into a plurality of thinner pieces of wood, and comprising a feed assembly for continuously feeding the stock from an upstream input position to a downstream output position, and a plurality of closely spaced-apart parallel reciprocable saw blades positioned intermediate the input position and the output position for sawing the stock into thinner pieces of stock as the stock is moved by the feed assembly relative to the blades. A drive assembly is operatively connected to the blades for driving the blades in a reciprocating motion comprising alternate cutting and non-cutting strokes. A linear offset motion assembly is provided for moving the reciprocating blades alternately upstream and downstream into linearly-offset cutting and non-cutting positions relative to the stock. Control means are provided for coordinating the reciprocating movement of the blades and the linear offset motion of the blades to thereby permit continuous movement of the stock while the blades are in both the cutting and non-cutting positions and strokes.
According to one preferred embodiment of the invention, the control means comprises an encoder for determining the reciprocation position of the blades, and a servo-motor responsive to position signals received from the encoder for moving the linear offset motion assembly linearly in timed relationship with the reciprocation of the blades.
According to another preferred embodiment of the invention, the saw blades reciprocate vertically between a cutting downstroke and a non-cutting upstroke.
According to yet another preferred embodiment of the invention, the linear offset motion assembly moves the saw blades linearly downstream away from the moving stock during the non-cutting stroke of the blades.
According to yet another preferred embodiment of the invention, a saw frame carriage is provided within which the saw blades are carried for reciprocation.
According to yet another preferred embodiment of the invention, the linear offset motion assembly includes first and second carriage arm assemblies connected to the saw frame carriage for pivotal movement with the reciprocation of the saw blades about respective pivot points, and the servo-motor moves the saw frame carriage alternately upstream and downstream into linearly-offset cutting and non-cutting positions relative to the stock by linearly moving the pivot points of the respective carriage arms in coordination with the reciprocating movement of the frame saw carriage.
According to yet another preferred embodiment of the invention, the carriage arm pivots are defined by respective pivot blocks mounted for linear movement.
According to yet another preferred embodiment of the invention, the pivot blocks are connected together by a connecting rod for unison movement.
According to one preferred embodiment of the invention, a frame saw is provided for sawing a relatively thick piece of wooden feed stock simultaneously into a plurality of thinner pieces of wood, and comprises a feed assembly for continuously feeding the stock from an upstream input position to a downstream output position, and a plurality of closely spaced-apart, parallel and vertically-reciprocable saw blades carried in a saw frame carriage positioned intermediate the input position and the output position for sawing the stock into thinner pieces of stock as the stock is moved by the feed assembly relative to the blades. The saw blades have teeth thereon angled to cut the stock on a cutting downstroke of the saw frame carriage. A drive motor is operatively connected to the saw frame carriage for driving the blades carried in the saw frame carriage in a reciprocating motion comprising alternate downward cutting and upward non-cutting strokes. A linear offset motion assembly is provided for moving the saw frame carriage alternately upstream and downstream into linearly-offset cutting and non-cutting positions relative to the stock.
Control means are provided for coordinating the reciprocating movement of the saw frame carriage and the linear offset motion of the saw frame carriage to thereby permit continuous movement of the stock while the blades are in both the cutting and non-cutting positions and strokes. The control means comprises an encoder for determining the reciprocation position of the saw frame carriage, and a servo device responsive to position signals received from the encoder for moving the linear offset motion assembly linearly in timed relationship with the reciprocation of the saw frame carriage.
According to yet another preferred embodiment of the invention, the servo device comprises a servo-motor and a rotary-to-linear motion apparatus for translating rotary motion of the servo-motor into a corresponding linear motion of the linear offset motion assembly.
Preferably, the rotary-to-linear motion apparatus comprises a ball screw assembly.
An embodiment of the method of sawing a relatively thick piece of wooden feed stock into thinner pieces according to the invention comprises the steps of continuously feeding the stock from an upstream input position to a downstream output position while simultaneously sawing the stock into a plurality of thinner pieces of stock as the stock is fed relative to the blades by driving the blades in a reciprocating motion comprising alternate cutting and non-cutting strokes. The reciprocating blades are moved alternately upstream and downstream into linearly-offset cutting and non-cutting positions relative to the stock. The reciprocating movement of the blades and the linear offset motion of the blades is coordinated to thereby permit continuous movement of the stock while the blades are in both the cutting and non-cutting positions and strokes.
According to yet another preferred embodiment of the invention, the method includes the steps of determining the reciprocation position of the blades, and moving the linear offset motion assembly linearly in timed relationship with the reciprocation of the blades.
According to yet another preferred embodiment of the invention, the step of reciprocating the blades comprises the step of reciprocating the blades vertically between a cutting downstroke and a non-cutting upstroke.
According to yet another preferred embodiment of the invention, the saw blades move linearly downstream away from the moving stock during the non-cutting stroke of the blades.
According to yet another preferred embodiment of the invention, the depth of cut of a single cutting stroke of the blades is equal to the sum of the downstream travel of the feed stock during the cutting stroke and the linear upstream travel of the blades from the non-cutting to the cutting position.